Intermediate alloy and process for forming wear-resistant cast iron



Patented July 27, 1954 UNITED STATES PATENT OFFICE INTERMEDIATE ALLOYAND PROCESS FOR FORMING WEAR-RESISTANT CAST IRON corporation of DelawareNo Drawing. Application May 15, 1952, Serial No. 288,007

8 Claims.

titanium. United States Patents Nos. 2,179,695

and 2,225,529], which issued November i, 1939, and November 24, 1940,respectively, in the name of Walter E. Jominy, disclosed examples ofthis type of cast iron. Heretofore, however, the use of titanium in castiron has been limited. by the difficulty encountered in introducing thetitanium into the melt because of the affinity of titanium for oxygenand nitrogen. Large quantities of slag are formed and a high percentageof the titanium is lost as a result of this aflinity.

Prior to the present invention these alloying components Were generallyadded separately in the form of ferro-titanium, silicon-titanium orferro-phosphorus alloys. Inasmuch as these alloys are high melting pointcombinations of elements, they must be subjected to a relatively hightemperature for a considerable period of time in order to place them insolution. Hence these hardening alloys necessarily are added directly tothe furnace. Such a procedure usually results in a titanium recovery,for example, of approximately only 50%. On the other hand, when theabove elements are combined in certain relatively low-meltingintermediate alloys and added to the ladle in accordance with myinvention, almost 100% of the titanium may be recovered because thephosphorus present in the intermediate alloy permits a rapid rate ofsolution which effectively precludes oxidation of the titanium.

It is therefore a principal object of my invention to provide anintermediate alloy containing titanium and phosphorus which can be addedto cast iron to increase its wear resistance. A

Q l further object of my invention is to provide a which a singleintermediate alloy containing titanium and phosphorus is added to theladle immediately prior to pouring molten cast iron; The presence oftitanium, together with phosphorus, in my intermediate alloy improvesthe wear resistance of the resultant cast iron by beneficially modifyingthe phosphorus eutectic. More specifically, I have found that titaniumlosses into the slag may be greatly reduced and the wear resistance ofthe cast iron accordingly increased if an intermediate ferrous-basealloy containing titanium and phosphorus is added to the molten castiron in the ladle immediately prior to casting. This ladle addition ispossible because of the relatively low melting point. of the alloy dueto the percentage of phosphorus present.

For optimum wear resistance, moreover, I. prefer to use a ferrous-baseintermediate alloy which contains minor proportions of nickel as well astitanium and phosphorus. The increased wear resistance of the finalcast, iron is principal- 1y due to the presence of a hard network of atitanium-containing phosphorus eutectic. Regardless of the exactchemical composition of this hard phase, its presence is primarilyresponsible for the further increase in Wear resistance. Hence thepesent invention provides a cast iron having physicial characteristicswhich satisfy all requirements of the aforementioned wearing parts.

Wear resistance, of course, is a function of both the size anddistribution of the aforementioned hard network. Inasmuch as the sizeand distribution of the network are dependent on such factors as themetal viscosity, solidification. rate and method of alloying, thepreferred procedure for preparing cast iron in accordance with myinvention provides a cast iron having maximum Wear resistance withminimum attrition. Thus, I have found that superior results are obtainedby introducing the phosphorus, nickel and titanium in the form of asolid phosphorus-nickel-titaniumiron intermediate alloy hardener.

An intermediate hardening alloy which I have found to be highlysatisfactory is one comprising 3.5% to 18% titanium, 15% to 35%phosphorus.

phosphorus and the balance substantially all iron provides the cast ironwith outstanding wear-resistance properties. In order to obtain optimumresults, however, I have found that the titanium content of heintermediate alloy should be maintained within a preferred range of 6%to 13% by weight of the intermediate alloy.

A very highly wear-resistant cast iron is produced when such a hardeneris introduced as a ladle addition to a ferrous base metal which, forexample, contains between 2.5% to 4% carbon, 1.5% to 3% silicon, 0.5% to1% manganese, and 0.1% to 1% chromium. This cast iron may also initiallycontain small quantities of nickel and phosphorus, these elementsfrequently being present in amounts in the order of 0.05% to 0.1% and0.05% to 0.25%, respectively. The intermediate alloy is preferably addedin an amount sufiicient to permit the aforementioned 3.5% to 18%titanium content to constitute between 0.05% and 0.35% of the final castiron. Eence a 1% to 2% alloy addition has proved effective to accomplishthis result.

Inasmuch as the quantity of the intermediate alloy employed is verysmall as compared with the amount of cast iron to which it is added, thepercentages of the alloying constituents original- 1y present in thecast iron remain substantially unaltered in the final alloy. Hence, acast iron comprising apprcximately 2.5% to 4% carbon, 1.5% to 3% slicon, 0.5% to 1% manganese, 0.1% to 1% chromium, 0.05% to 0.35%titanium, 0.3% to 0.7% phosphorus and the balance substantially all ironpossesses a high degree of wear resistance. If the aforementionedproportion of nickel is substituted for an equivalent amount of iron inthe intermediate alloy, the resultant very highly wear-resistant castiron preferably contains 0.1 to 0.45% nickel. As hereinbefore stated,excellent results are obtained with an intermediate alloy having atitanium content between and 13%, and the use of this preferred hardeneralloy composition results in a final cast iron which contains 008% to0.15% titanium.

For particular purposes it may be desirable to include a small amount ofvanadium in the cast iron and, if this is done, it should be included inthe original ferrous metal melt in an amount between 0.05% to 0.15%.This vanadium content is approximately the same both before and afterthe hardening alloy addition because of the relatively small amount ofthe intermediate alloy required. It will be understood, of course, thatthe cast iron formed may also contain other incidental impurities suchas sulfur, but for best results the sulfur content should not exceedapproximately 0.2%.

As an example of a specific nickel-containing intermediate alloy whichmay be used in accordance with my improved process to provide a highlywear-resistant cast iron, one containing 9.1% titanium, 9.1% nickel,20.4% phosphorus and the balance iron has proved to be highlysatisfactory. This alloy is added in an amount calculated to yieldapproximately 0.15% titanium in a cast iron containing 3.2% carbon, 2.5%silicon, 0.75% manganese and 0.35% chromium. Approximately 0.1% vanadiummay also be included in the original cast iron melt and provides a finalcasting which has good working properties as well as high wearresistance.

When the above-described intermediate alloy is added to the ladlecontaining the aforementioned ferrous metal immediately prior to thepouring operation, the resultant cast iron has been found to beconsiderably more wear-resistant than the same ferrous metal to whichthe intermediate alloy has not been added. As an illustration of theimproved physical properties of the former, wear test samples of theabove-described cast iron formed in accordance with my invention andcast into sand-resin molds yield an average wear loss of between 0.012gram and 0.016 gram when tested in a standard wear test machine. Thesewear losses indicate results which are superior to those obtained withthe same initial cast iron to which my titaniumphosphorus-nickel-ironintermediate alloy has not been added. The latter cast iron shows wearlosses which are between approximately two and three times as great asthose obtained with my improved cast iron. For example, using the samewear testing procedures and equipment indicated above, the cast ironsamples containing no titanium, phosphorus or nickel show an averagewear loss between 0.035 and 0.06 gram.

The results of the above and other tests on cast irons prepared inaccordance with my inention and containing as little as 0.05% titaniumshow that the above-described intermediate alloy imparts to cast iron awear resistance superior to conventional cast irons whichconconsiderably more titanium in the final casting. An even greateramount of titanium must be initially added in these latter instances,moreover, because of the low titanium recoveries resuiting from theseparate addition of the alloying components. Hence, it should be notedthat adding titanium, phosphorus and iron in the form of my complexalloy not only permits the ladle addition of titanium and therebysubstantially increases the percentage of titanium recovered, butprovides the cast iron with a wear resistance superior to obtained bythe separate addition of the alloying ingredients.

Except as otherwise indicated, the exact alloying procedure to beemployed with reference to temperatures used and mechanical steps to betaken may be conventional in nature and, being well known in the art,requires no further expianation. However, inasmuch as it is desirable tocast the intermediate alloy in shapes which will dissolve most readilyin the molten cast iron, I fii d it advantageous to form intermediatealloy castings having a high ratio of surface area to volume, such ascrushed material having particle diameters of 2 inch or less. It will beunderstood, of course, that this intermediate alloy can be added inother forms, but that the above procedure facilitates the alloyingoperation and results in maximum titanium recovery. Any suitable meltingfurnace may be used; and normal tapping temperatures may be employed,such as those between 2700 F. and 3000 F.

it also will be understood that, although my invention has beendescribed my means of certain specific examples of cast irons andintermediate alloys for forming cast iron characterized by high wearresistance, the scope of my invention is not to be limited therebyexcept as defined in the appended claims.

I claim:

1. A method of forming a highly wear-resistant cast iron which comprisesadding to the ladle immediately prior to pouring an intermediate alloycontaining minor proportions of titanium and phosphorus.

2. A method of forming a highly wear-resistant cast iron which includesadding to a ladle containing cast iron immediately prior to pouringoperations an alloy comprising approximately 3.5% to 18% titanium,approximately to 35% phosphorus, and the balance substantially all iron.

3. In the production of wear-resistant cast iron, the improvement whichcomprises the step of adding to a ladle containing iron and the usualiron alloying ingredients an intermediate alloy comprising about 3.5% to18% titanium, about 6% to 13% nickel, about 15% to 35% phosphorus, andthe balance substantially all iron.

4. A method of forming a highly wear-resistant cast iron which comprisesadding to cast iron an intermediate alloy comprising approximately 3.5%to 18% titanium, 6% to 13% nickel, 15% to 35 phosphorus and the balanceiron, said intermediate alloy being added to the ladle immediately priorto pouring operations in an amount constituting between 1% and 2% byweight of the final cast iron.

5. The method of producing a highly Wearresistant cast iron whichincludes melting in a furnace a mixture comprising approximately 2.5% to4% carbon, 1.5% to 3% silicon, 0.5% to 1% manganese, 0.1% to 1% chromiumand the balance substantially all iron, transferring said molten mixtureto a ladle, subsequently adding to said ladle immediately prior topouring operations an intermediate alloy in the solid state in an amountconstituting between 1% and by weight of the final cast iron, saidintermediate alloy consisting essentially of 6% to 13% titanium, 6% to13% nickel, 15 to phosphorus and 39% to 73% iron, permitting said alloyto melt in said ladle, and thereafter casting the resultant moltenmixture.

6. A composition of matter for addition to ferrous metals to providehigh wear resistance thereto, said composition comprising approximately3.5% to 18% by weight of titanium, approximately 15% to 35% by weight ofphosprorus and the balance subsctantially all iron.

7. An intermediate alloy for addition to ferrous metals to provide highwear resistance thereto, said alloy comprising about 3.5% to 18%titanium, about 6% to 13% nickel, about 15% to 35% phosphorus, and thebalance substantially all iron.

8. An intermediate alloy for ladle addition to molten cast ironimmediately prior to pouring operations, said alloy consistingessentially of 6% to 13% titanium, 6% to 13% nickel, 15% to 35%phosphorus, and 39% to 73% iron.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,137,863 Strauss Nov. 22, 1938 2,169,193 Comstock Aug. 8,1939

2. A METHOD OF FORMING A HIGHLY WATER-RESISTANT CAST IRON WHICH INCLUDESADDING TO A LADLE CONTAINING CAST IRON IMMEDIATELY PRIOR TO POURINGOPERATIONS AN ALLOY COMPRISING APPROXIMATELY 3.5% TO 18% TITANIUM,APPROXIMATELY 15% TO 35% PHOSPHORUS, AND THE BALANCE SUBSTANTIALLY ALLIRON.